On Tue, 27 Mar 2018 12:05:09 -0700, Bob La Londe
wrote:

A buddy of mine called me yesterday saying he was having some troubles
seating tools in his new bench top mill. I stopped by to see if I could
help and I found there appeared to be only a thin ring of contact
surface very near the large end of the taper on every tool and collet.
So little that tools tightened down HARD just fell right out when the
draw bar was loosened. Its supposed to be an R8 spindle and came with a
few R8 tools.

That sounds a lot like the wrong taper fit to inexperienced me, too.


So how much contact surface should I expect to see between and R8
spindle and an R8 shank tool?

I just found out that there are self-holding and self-releasing
classes of tapers. It seems that I have a lot to learn.
https://en.wikipedia.org/wiki/Machine_taper . According to that,
Morse tapers are the self-holding style, so it certainly seems that he
has mismatched tooling/spindle tapers.


I have had one mill with an R8 spindle and if I had tightened a collet
into it as hard as I had to to tighten tools into his mill it would have
taken several hammer blows on the draw bar to knock them loose.

This is my buddy's second mill with an R8 spindle and tools he was
struggling with on this one seated easily and worked just fine on his
old one.

I wondered if maybe he got a spindle with an MT taper by mistake but my
uneducated finger says it feels like the wide taper angle of an R8, and
not the shallow taper angle of an MT. I do have some misc sizes of MT
taper tools for my lathe. I guess I could head over and see if they are
a better fit just to be safe.

Excellent idea. But remember that there are many different tapers. If
you have inside calipers, you could measure it and get a good idea.
The chart on the wiki page should guide you.

Perhaps your buddy can get the seller (dealer?) to replace the tooling
if you find that it's mismatched.

--
"I have noticed even people who claim everything is predestined
and that we can do nothing to change it look before they cross
the road." --Steven Hawking